Commentary on "Perspective on race and ethnicity in Alzheimer's disease research".

There are persistent disparities in Alzheimer's disease by race and ethnicity that are not well understood. The emphasis given to seeking a genetic basis for racial differences might be a distraction from the more relevant issue of identifying preventable causes of Alzheimer's disease. The majority of Alzheimer's disease cases are diagnosed as the late onset type and are unlikely to be inherited. Late onset Alzheimer's disease cases, therefore, more likely represent variations in gene expression than gene frequency. Although conceptual and methodologic problems have limited our understanding of this relationship, race-based studies provide important opportunities to understand the environmental factors associated with gene expression. Improving our understanding of the factors associated with race and ethnicity might help to clarify the epidemiology and course of Alzheimer's disease.

Association of Long Runs of Homozygosity With Alzheimer Disease Among African American Individuals.

IMPORTANCE: Mutations in known causal Alzheimer disease (AD) genes account for only 1% to 3% of patients and almost all are dominantly inherited. Recessive inheritance of complex phenotypes can be linked to long (>1-megabase [Mb]) runs of homozygosity (ROHs) detectable by single-nucleotide polymorphism (SNP) arrays. OBJECTIVE: To evaluate the association between ROHs and AD in an African American population known to have a risk for AD up to 3 times higher than white individuals. DESIGN, SETTING, AND PARTICIPANTS: Case-control study of a large African American data set previously genotyped on different genome-wide SNP arrays conducted from December 2013 to January 2015. Global and locus-based ROH measurements were analyzed using raw or imputed genotype data. We studied the raw genotypes from 2 case-control subsets grouped based on SNP array: Alzheimer's Disease Genetics Consortium data set (871 cases and 1620 control individuals) and Chicago Health and Aging Project-Indianapolis Ibadan Dementia Study data set (279 cases and 1367 control individuals). We then examined the entire data set using imputed genotypes from 1917 cases and 3858 control individuals. MAIN OUTCOMES AND MEASURES: The ROHs larger than 1 Mb, 2 Mb, or 3 Mb were investigated separately for global burden evaluation, consensus regions, and gene-based analyses. RESULTS: The African American cohort had a low degree of inbreeding (F ~ 0.006). In the Alzheimer's Disease Genetics Consortium data set, we detected a significantly higher proportion of cases with ROHs greater than 2 Mb (P = .004) or greater than 3 Mb (P = .02), as well as a significant 114-kilobase consensus region on chr4q31.3 (empirical P value 2 = .04; ROHs >2 Mb). In the Chicago Health and Aging Project-Indianapolis Ibadan Dementia Study data set, we identified a significant 202-kilobase consensus region on Chr15q24.1 (empirical P value 2 = .02; ROHs >1 Mb) and a cluster of 13 significant genes on Chr3p21.31 (empirical P value 2 = .03; ROHs >3 Mb). A total of 43 of 49 nominally significant genes common for both data sets also mapped to Chr3p21.31. Analyses of imputed SNP data from the entire data set confirmed the association of AD with global ROH measurements (12.38 ROHs >1 Mb in cases vs 12.11 in controls; 2.986 Mb average size of ROHs >2 Mb in cases vs 2.889 Mb in controls; and 22% of cases with ROHs >3 Mb vs 19% of controls) and a gene-cluster on Chr3p21.31 (empirical P value 2 = .006-.04; ROHs >3 Mb). Also, we detected a significant association between AD and CLDN17 (empirical P value 2 = .01; ROHs >1 Mb), encoding a protein from the Claudin family, members of which were previously suggested as AD biomarkers. CONCLUSIONS AND RELEVANCE: To our knowledge, we discovered the first evidence of increased burden of ROHs among patients with AD from an outbred African American population, which could reflect either the cumulative effect of multiple ROHs to AD or the contribution of specific loci harboring recessive mutations and risk haplotypes in a subset of patients. Sequencing is required to uncover AD variants in these individuals.

Depression as a risk factor for Alzheimer disease: the MIRAGE Study.

BACKGROUND: Depression symptoms may be associated with the development of Alzheimer disease (AD). OBJECTIVES: To evaluate the association between depression symptoms and risk of AD, and to explore the temporal aspects of this association. SETTING: Academic institutions with specialized memory clinics. DESIGN: Cross-sectional, family-based, case-control study with standardized self- and proxy questionnaires to collect information on depression symptoms and other risk factors. PARTICIPANTS: A total of 1953 subjects with AD and 2093 of their unaffected relatives enrolled in the Multi-institutional Research in Alzheimer's Genetic Epidemiology Study. MAIN OUTCOME MEASURES: Odds ratios (ORs) of AD were estimated with and without depression symptoms, adjusted for age, sex, education, history of head trauma, and apolipoprotein E status. RESULTS: There was a significant association between depression symptoms and AD (adjusted OR, 2.13; 95% confidence interval [CI], 1.71-2.67). In families where depression symptoms first occurred within 1 year before the onset of AD, the association was higher (OR, 4.57; 95% CI, 2.87-7.31), while in the families where the depression symptoms first occurred more than 1 year before the onset of AD, the association was lower (OR, 1.38; 95% CI, 1.03-1.85). In families where depression symptoms first occurred more than 25 years before the onset of AD, there was still a modest association (OR, 1.71; 95% CI, 1.03-2.82). CONCLUSIONS: Depression symptoms before the onset of AD are associated with the development of AD, even in families where first depression symptoms occurred more than 25 years before the onset of AD. These data suggest that depression symptoms are a risk factor for later development of AD.

The art of sharing the diagnosis and management of Alzheimer's disease with patients and caregivers: recommendations of an expert consensus panel.

OBJECTIVE: To develop a set of recommendations for primary care physicians (PCPs) suggesting how best to communicate with patients, caregivers, and other family members regarding the diagnosis and management of Alzheimer's disease (AD). PARTICIPANTS: A national roundtable of 6 leading professionals involved in treating or advocating for patients with AD was convened on March 14, 2008. This roundtable included 4 leading academic physicians with diverse backgrounds (a geriatric psychiatrist, a neuropsychiatrist, a neurologist, and a geriatrician) from geographically diverse regions of the United States, who were invited on the basis of their national reputation in the field and experience working with minority populations with dementia; the executive director of a national AD advocacy organization; the executive director of a national advocacy organization for caregivers; and a medical correspondent with expertise in interviewing and small group leadership. EVIDENCE: Expert opinion supported by academic literature (search limited to PubMed, English language, 1996-2008, search terms: Alzheimer's disease, primary care, diagnosis, management, caregiver, family, patient-physician relationship). CONSENSUS PROCESS: Moderated dialogue aimed at generating consensus opinion; only statements endorsed by all authors were included in the final article. CONCLUSIONS: Diagnosis and management of AD by PCPs, utilizing specialist consultation as needed, may contribute to earlier diagnosis and treatment, improved doctor-patient and doctor-caregiver communication, increased attention to caregiver needs, and better clinical and quality-of-life outcomes for patients and caregivers. A set of expert panel recommendations describing practical strategies for achieving these goals was successfully developed.

Risk of dementia among white and African American relatives of patients with Alzheimer disease.

CONTEXT: Evidence exists that the incidence of Alzheimer disease (AD), as well as risk attributable to specific genetic factors such as apolipoprotein E (APOE) genotype, may vary considerably among ethnic groups. Family studies of probands with AD offer an opportunity to evaluate lifetime risk of dementia among relatives of these probands. OBJECTIVE: To compare lifetime dementia risk estimates among relatives of white and African American probands with probable or definite AD. DESIGN AND SETTING: Risk analysis using data collected by questionnaire and supplemental records between May 1991 and March 2001 at 17 medical centers contributing to the Multi-Institutional Research in Alzheimer's Genetic Epidemiology Study. PARTICIPANTS: A total of 17 639 first-degree biological relatives and 2474 spouses of 2339 white AD probands, and 2281 first-degree biological relatives and 257 spouses of 255 African American AD probands. MAIN OUTCOME MEASURES: Cumulative risk of dementia by age 85 years, stratified by ethnicity and sex of relatives and by APOE genotype of probands. RESULTS: Cumulative risk of dementia in first-degree biological relatives of African American AD probands by age 85 years was 43.7% (SE, 3.1%), and the corresponding risk in first-degree biological relatives of white AD probands was 26.9% (SE, 0.8%), yielding a relative risk (RR) of 1.6 (95% confidence interval [CI], 1.4-1.9; P<.001). The risk in spouses of African American AD probands of 18.5% (SE, 8.4%) was also higher than the risk in white spouses of 10.4% (SE, 1.7%) but did not reach statistical significance (RR, 1.8; 95% CI, 0.5-6.0; P =.34), likely due to the smaller sample size of African Americans. The proportional increase in risk of dementia among white first-degree biological relatives compared with white spouses of 2.6 (95% CI, 2.1-3.2) was similar to that of 2.4 (95% CI, 1.3-4.4) in African American first-degree biological relatives compared with African American spouses. Female first-degree biological relatives of probands had a higher risk of developing dementia than did their male counterparts, among whites (31.2% vs 20.4%; RR, 1.5; 95% CI, 1.3-1.7; P<.001) as well as among African Americans, although this was not significant among African Americans (46.7% vs 40.1%; RR, 1.2; 95% CI, 0.9-1.7, P =.30). The patterns of risk among first-degree biological relatives stratified by APOE genotype of the probands were similar in white families and African American families. CONCLUSION: First-degree relatives of African Americans with AD have a higher cumulative risk of dementia than do those of whites with AD. However, in this study, the additional risk of dementia conferred by being a first-degree relative, by being female, or by the probability of having an APOE epsilon4 allele appeared similar in African American and white families. These data provide estimates of dementia risk that can be used to offer counseling to family members of patients with AD.